If you want to alter the original objects, then a simple Array#forEach will do:
rockets.forEach(function(rocket) {
rocket.launches += 10;
});
If you want to keep the original objects unaltered, then use Array#map and copy the objects using Object#assign:
var newRockets = rockets.forEach(function(rocket) {
var newRocket = Object.assign({}, rocket);
newRocket.launches += 10;
return newRocket;
});